Operation of an ISFET with non-insulated substrate directly exposed to the solution

✍ Scribed by A.A. Shul'ga; L.I. Netchiporouk; A.K. Sandrovsky; A.A. Abalov; O.S. Frolov; Yu.G. Kononenko; H. Maupas; C. Martelet

• Book ID: 103961181
• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 565 KB
• Volume: 30
• Category: Article
• ISSN: 0925-4005
• DOI: 10.1016/0925-4005(95)01760-s

✦ Synopsis

The use of a probe-type n-channel depletion-mode Si3N4-ISFET with the substrate in direct contact with solution is described. A proper mode of ISFET operation is achieved when it is electrically isolated from the solution by a reversely biased diode formed by an n-type sourcechannel--drain region and a p-type substrate. The ohmic contact used to bias the substrate is at the same time utilized to short-circuit the photovoltage generated at the p-n junction in order to reduce the ISFET light sensitivity. The pH sensitivity of the ISFETs is linear with a slope 55 -1-1.5 mV pH-t (n =6) in the pH range 2 to 10. In the case of cell and enzyme biosensors based on a differential pair of ISFETs, the non-encapsulated substrate of the sensor chip itself may be used as a quasi-reference electrode.